Colorize is very good tool for simply piping your text through another filter to get fancy ANSI colors. In fact, it's one simple 4kB perl script (almost half of it is just documentation) and it's based on regular expressions.

You can highlight whole line containing given patern (good for hiding unwanted debug logs or highlighting Exceptions) or just highlight pattern in uncolored line (highlighting http response codes).

I have several presets for various file types in separate runnable files. Then I just run mvn clear install | colorbuild, tail -f *.log* | colorlog or svn diff | colordif to have really fancy output.